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NFPA 704 is the official name for Fire Diamonds, which are rhombus-shaped sign that has 4 different colored squares that tell you how dangerous a substance is in four ways: Health (Blue), Reactivity (Yellow), Flammability (Red) and the white square is for Miscellaneous hazards. Each colored square is marked with a number ranging between zero and four. Zero/Empty means that that substance has no danger in that category. 1 = mildly hazardous, 2 = hazardous, 3 = extremely hazardous, and 4 = Lethal.
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